Advances in microvascular decompression for hemifacial spasm

Primary hemifacial spasm(HFS) is a disorder that causes frequent involuntary contractions in the muscles on one side of the face, due to a blood vessel compressing the nerve at its root exit zone(REZ) from the brainstem. Numerous prospective and retrospective case series have confirmed the efficacy of microvascular decompression(MVD) of the facial nerve in patients with HFS. However, while MVD is effective, there are still significant postoperative complications. In this paper, recent technological advances related to MVD(such as lateral spread response,brainstem auditory evokes potential, three dimensional time of flight magnetic resonance angiography, intraoperative neuroendoscopy) are reviewed for the purposes of improving MVD treatment efficacy and reducing postoperative complications.

EXPRESSION OF CALCITONIN GENE-RELATED PEPTIDE IN FACIAL NERVE OF HEMIFACIAL SPASM

Objective To study the immunoreactivity of Calcitonin gene-related peptide (CGRP) in the facial nerve when Hemifacial Spasm is occurring. Methods The electrophysiological technique was used to explore abnormal muscle response (AMR) which was characteristic of Hemifacial Spasm.The animal models of Hemifacial Spasm in New Zealand white rabbits were established by compressing the main trunk of artificial demyelinated facial nerve with the temporal superficial artery. At 6 weeks after surgery, the facial nerves were taken from the experimental group and control one, the immunohistochemistry for CGRP using polyclonal antibody with ABC kit was performed in the facial nerves; at the same time, the observation for the facial nerves of light and transmission electron microscope was performed. Results The facial nerve demyelinated and the axons retrogressively changed, CGRP immunoreactive positive fibers were significantly detected in experimental groups; whereas this phenomenon was not found in control group. Conclusion CGRP can nutrien the injured facial nerve and plays an important role in the pathogenesis of Hemifacial Spasm.

Complications of microvascular decompression in hemifacial spasm treatment Retrospective analysis of 156 cases

BACKGROUND： Microvascular decompression has become a well-accepted, safe method in the treatment of hemifacial spasms. However, postoperative complications exist and influence the prognosis of the disease. OBJECTIVE： This study aimed to analyze, by case review, the characteristics and regularity of microvascular decompression complications in the treatment of hemifacial spasm. DESIGN： Retrospective analysis. SETTING： Beijing General Group Hospital of the Chinese People＇s Armed Police Forces. PARTICIPANTS： A total of 156 patients with hemifacial spasm were admitted to the Department of Neurosurgery, Beijing General Group Hospital of the Chinese People＇s Armed Police Forces from June 2004 to June 2006 and recruited for this study. The patients, 57 males and 99 females, averaged 46 years of age （range 17-68-years old）. All suffered from facial innervated muscular paroxysmal and recurrent contraction, which could not be controlled by consciousness. Electromyogram demonstrated waves of fibrillation and fasciculation. Prior to admission, all patients had received other treatments. Written informed consents for treatment were obtained from all patients. This protocol was approved by the Hospital＇s Ethics Committee. METHODS： After anesthesia, a cranial bone pore was drilled below the connection of the lateral sinus and sigmoid sinus. Dura mater was dissected at the ＂⊥＂ shape and held in the air. Under microscopy, the flocculus cerebelli was lifted slightly up for convenient observation of the cerebellopontine angle. The mucous membrane was sharply separated. Corresponding vessels were identified at the root of the facial nerves and subsequently liberated and disassociated from the root exit zone. Suitably sized Teflon cotton was placed between the corresponding vessels and brain stem. MAIN OUTCOME MEASURES： Complications of microvascular decompression. RESULTS： All 156 patients participated in the final analysis. （1） Postoperatively, 66 （42%） patients presented with obvious headache or dizziness, 5 （3%） with severe headache, 43 （28%） with nausea or vomiting for 12 hours to 3 days, and 19 （12%） with aseptic meningitis and a body temperature of 37.5-40 ℃ Patients, who suffered from headache and fever, were cured after 2-5 lumbar punctures. （2） Postoperatively, 19 （8%） patients suffered from short-term dysaudia and tinnitus on the affected side, 9 （6%） from mild hemifacial spasms, and 2 （1%） from ambiopia. All patients were cured after treatment with a neurotrophic drug. （3） Postoperatively, 4 （2%） patients suffered from cerebrospinal fluid incision leakage and 2 （1%） from cerebrospinal rhinorrhea. The cerebrospinal fluid incision was tightly sutured. One case of cerebrospinal rhinorrhea was cured after mastoid process repair, and the other one recovered spontaneously. CONCLUSION： Experimental results have indicated that low intracranial pressure is the main complication of microvascular decompression in patients with hemifacial spasms, and no permanent neuro-functional impairment was found.

The value of abnormal muscle response monitoring during microvascular decomprssion surgery for hemifacial spasm

Objective Abnormal muscle response (AMR) to the electrical stimulation of a branch of facial nerve is a specific electrophysiological feature of primary hemifacial spasm (HFS) . Although the correlation between intraoperative AMR findings and postoperative results in patients with HFS were investigated before,

Influence of distal portion compression of facial nerve in hemifacial spasm surgery

Objective To study influence of distal portion compression of facial nerve in hemifacial spasm surgery. Methods 120 hemifacial spasm patients were undergone lateral spread response monitoring during microvascular decompression surgery. 39 patients’LSR remained after decompression of the root exit zone of the facial nerve.

Clinical features and treatment status of hemifacial spasm in China

Background Hemifacial spasm （HFS） is a facial nerve disorder characterized by episodic involuntary ipsilateral facial muscle contraction.Information on Chinese patients with HFS has not been well-characterized.This study aimed to evaluate the clinical feature and the treatment status of HFS across China.Methods A cross-sectional study including 1003 primary HFS patients had been carried out in 15 movement disorder clinics in China in 2012.The investigated information was acquired from questionnaires and medical records including demographic data,site of onset,aggravating and relieving factors,treatments prior to the investigation,etc.Results In this study,the ratio of male to female was 1.0：1.8,the mean age at onset was （46.6±11.5） years.About 1.0％ patients were bilaterally affected.The most often site of initial onset was the orbicularis oculi muscle.The most often affected sites were orbicularis oculi,zygomatic,and orbicularis oris muscles.Stress/anxiety and relaxation were most often aggravating and relieving factors,respectively; 2.3％ patients had family history,28.4％ cases were combined with hypertension,and 1.4％ patients were with trigeminal neuralgia.Botulinum toxin type A （BTX-A） injection was the most commonly used treatment,followed by acupuncture and oral medication.BTX-A maintained the highest repeat treatment ratio （68.7％）,while 98.4％ patients gave up acupuncture.The mean latency of BTX-A effect was （5.0±4.7） days,the mean total duration of the effect was （19.5±11.7） weeks,and 95.9％ patients developed improvements no worse than moderate in both severity and function.The most common side effect was droopy mouth.Conclusions The onset age of HFS in China is earlier than that in western countries.The most often used two treatments are BTX-A injection and acupuncture,while the latter kept the poor repeat treatment ratio because of dissatisfactory therapeutic effect.

Microvascular decompression in patients with hemifacial spasm: report of 1200 cases

Background Microvascular Decompression (MVD) operation is the most reliable treatment for hemifacial spasm (HFS), but it causes many complications. The aim of this retrospective study was to investigate the factors relavent to the effects and postoperative complications of microvascular decompression on hemifacial spasm. Methods A total of 1200 HFS patients treated with MVD were studied retrospectively. The root exit zone (REZ) of the facial nerve was exposed through the infraflocculus approach, the offending vessels were identified and separated from the REZ, and a Teflon graft was interposed between the offending vessels and the brain stem. Brain stem auditory evoked potential (AEP) was monitored intraoperatively. Results The offending vessels can be identified in all patients. The anteroinferior cerebellar artery was the main offending vessel (42.6%). Patients with vertebral artery compression had a multiple vascular compression fashion. Follow-up for 2-10 years (mean 4.2 years) showed that 88.7% patients were cured and 5.6% relieved, with an effective rate of 94.3%. Recurrence rate was 3.2%, and the ineffective rate was 2.6%. The most frequent complication was hearing dysfunction (2.8%). Conclusions MVD is the most definitive treatment method of HFS. The key procedures of this operation include adequate exposure of the REZ, identification of the offending vessels, and proper positioning of Teflon grafts. Complications can be reduced effectively by utilizing a real-time AEP monitoring during the operation.

Inter-Observer Reliability of Fused Time-of-Flight MR Angiography and 3D Steady State Sequence versus 3D Contrast Enhanced Images in Evaluation of Neurovascular Compression

Purpose: Is to evaluate the accuracy of fused 3D time-of-flight (TOF) MR angiography and 3D Steady-State sequence (FIESTA) versus 3D contrast-enhanced T1 weighted images in evaluation of neurovascular compression via an inter-observer agreement protocol. Methods: Patients presented with trigeminal neuralgia, tinnitus, or facial hemispasm were examined using 3D-TOF-MRA, 3D-FIESTA, and 3D contrast-enhanced T1WI of the cerebellopontine angle to assess neurovascular compression. Two independent readers assessed the location, signal alteration, offending vascular structure, and grade of neurovascular compression using fused 3D-TOF-MRA and 3D-FIESTA versus contrast-enhanced T1 weighted images. The Kappa test for interobserver agreement was done. Results: The final study cohort consisted of 56 patients (42 females and 14 males) with a mean age of 38.25 ± 1.94. AICA was the offending vessel for 32 (57.1%) patients. The most common offending nerve was the trigeminal nerve in 26 patients, followed by facial/vestibulocochlear complex in 18 patients, and solely the 8th nerve in 12 patients. All three grades of compression were encountered in this study with percentages of 48.2% (27/56), 30.3% (17/56), and 21.4% (12/56) for grades I, II, III respectively. Fused TOF and steady-state images, and contrast-enhanced images showed perfect agreement for detection of the side of compression, the relation between nerve and vascular loop, offended neural segment, and offending vessel, while showing good agreement regarding the degree of compression. Conclusion: Fused TOF and steady-state images provide sufficient data to diagnose and grade microvascular compression syndromes comparable to contrast-enhanced images.

The ideal microvascular decompression technique should be easy and safe

Microvascular decompression(MVD) surgery has been popularized as an etiological treatment around the world for more than half a century. However, as a functional operation in the cerebellopontine angle, this process should be refined to enhance cure and minimize complication. After accomplishing more than 10,000 MVDs, we have learned the following concerning the operative technique:(1) the principle of MVD is to separate the neurovascular confliction, rather than isolate with prostheses;(2) identification of the conflict relies on good exposure;(3) a satisfactory working space can be created by the appropriate positioning, i.e., either a close-to-the-sigmoid craniectomy or caudorostral approach;(4) a sharp dissection of arachnoids leads to a maximal visualization of the entire intracranial course of the nerve root;(5) all vessels contacting the trigeminal nerve root should be cleared off;(6) intraoperative electrophysiological monitoring may predict the prognosis of hemifacial spasm and guide the operation; and(7) the dura must be closed with watertight stitches at the end.